Audio distribution systems, especially those commonly used in outdoor speakers, etc., may require that many loudspeakers be driven from a single audio amplifier over long runs of speaker wire. It may be possible to connect 20 or 30 speakers in series/parallel combinations to achieve an acceptable impedance load of the speakers to the amplifier. However, this type system can be difficult to install and troubleshoot, and can be unreliable and inflexible to later modification. A “constant-voltage” or “high-impedance” audio distribution system is often used to overcome these and a number of other possible problems. These systems may be referred to by their nominal voltage, with “70-Volt” and “25-Volt” systems being the most common references.
In a typical 70 volt systems an impedance and voltage transformation is performed that allows the single amplifier to drive many speakers. Amplifiers that are designed for these systems may differ from “standard” audio power amplifiers in that they employ a large transformer at the output of the amplifier.
Attached to each speaker in a 70V system is typically another transformer that changes the power back to lower voltage/higher current from the input of a higher voltage (70) and lower current, suitable to drive the 8-ohm speaker attached to it-a so called 70 volt to 8 ohm conversion as used in the industry. Such transformers may usually have two output taps, one for 8-ohm speakers, and one for 4-ohm speakers.
However, in spite of the usefulness of 70 Volt systems in speaker systems, 70 volt systems they are considered high voltage according to typical building codes which is a disadvantage in installing such systems since extra care and expertise may be required. It would be desirable to find a way to configure an outdoor audio system such that users, and installers are isolated from the 70 Volt portion of the audio system, and only exposed to safer lower voltages.